GPU invert node

[Firestar99]

Code below shows how much I had to change the gpu invert node. Most of the changes are due to not wanting to depend on gcore, as it currently doesn't compile for no_std. I think we could probably get away without changing it at all. https://github.com/GraphiteEditor/Graphite/blob/bf2673428ae3260e4b55204bc930ab01ed8591d3/node-graph/gcore-shader/src/gpu_invert.rs#L4-L23

The rust-gpu shader calling it: https://github.com/GraphiteEditor/Graphite/blob/bf2673428ae3260e4b55204bc930ab01ed8591d3/node-graph/gcore-shader/src/gpu_invert.rs#L33-L38

[Firestar99]

The linker is erroring due to the wasm-specific flags somehow ending up in a native compile, probably env leaking again. Doesn't trigger locally, likely due to me using the mold linker. Will play around with it a bit more tomorrow.

[Keavon]

Ready to be rebased on master now.

[Firestar99]

Superseded by https://github.com/GraphiteEditor/Graphite/pull/3097 and https://github.com/GraphiteEditor/Graphite/pull/2985